Electrical receptacles, also known as outlets, wall plugs, etc., which in residential applications are commonly found mounted in an outlet box fixed within a wall and attached by terminals to an insulated powerline. By example, the typical powerline used for residential purposes has a line that has three wires, the first conducts the AC power wave, which is commonly known as the “hot”, the second this a return line, commonly referred to as “neutral” and a solid copper conductor commonly referred to as “ground”.
The typical receptacle has two parallel slots, and a third opening for the ground; behind each is a contact. Spades, also referred to as prongs, extending from a plug, conduct power by engaging the contacts. When the receptacle is connected to the line and the circuit is energized, the contacts are live. Safety, energy conservation and clean power (consistent power with low noise) are all concerns today with respect to electrical power. Monitoring power is the solution to all three concerns.
Measuring energy is routinely accomplished by use of power meters and has been enhanced to the benefit of the utility companies by the use of smart metering to measure total power consumption in real time. None of the concerns: safety, energy conservation, or power quality is addressed through smart metering. Energy monitoring systems in the current state-of-the-art make several troubling assumptions. First, the state-of-the-art assumes a site, whether it be residential, commercial or industrial, are wired correctly. Second, state-of-the-art metering systems assume the devices in the network are functioning correctly. And third, state-of-the-art metering systems fail to indicate how much energy is being consumed by a device or whether that device is functioning properly.
Electrical safety is a concern which is not addressed by state-of-the-art metering systems. A common safety concern is electrical shock resulting from insertion of an object into one of the receptacle slots. The art is replete with solutions to the threat of potential electrocution associated with a child inserting a conductive object in the receptacle.
There are multiple solutions in the art consisting of covers and inserts to prevent electrical shock. However these devices may become damaged and worn from the constant insertion and removal, which may also lead to neglecting their use altogether. In addition, small children may also pry off the covers to discover the mystery that lies beneath.
One such solution to this problem is disclosed in U.S. Pat. No. 7,312,394, entitled “Protective device with tamper resistant shutters”. The '394 patent discloses a receptacle cover assembly having a shutter. The shutter is movable to an open position by the insertion of at least one plug blade having a predetermined geometry. Although the '394 patent offers a measure of protection, it has no power shut off safety feature, which would prove critical if an object other than a plug blade were able to deceive the device.
To prevent electrical shock in bathrooms, building codes require the use of ground fault interrupt “GFI” receptacles. In principle, these devices operate by measuring the current difference between the hot and neutral lines. If a threshold difference is reached a switch is opened and conduction to the contacts within the receptacle is terminated.
One such device is disclosed in U.S. Pat. No. 7,227,435 entitled “GFCI without bridge contacts and having means for automatically blocking a face opening of a protected receptacle when tripped”. The '435 patent discloses a device which prevents insertion of the prongs of a plug when the GFI circuit is tripped in the event of mis-wiring or a switch failure. When the device is tripped, an arm moves downward causing the contact to open and a blocking member is moved to a blocking position. However, a concern with this system is in the event of a failure, the contact will not open, nor will the blocking member be moved into the blocking position.
One solution to the failing GFI switch is disclosed in U.S. Pat. No. 7,317,600 entitled “Circuit interrupting device with automatic end of life test”. The '600 patent discloses a GFI circuit capable of simulating a ground fault to determine whether the device is working properly. An integrated circuit chip is connected to switch that interacts with the reset button. A user can determine whether the device has failed by engaging the reset button. However, the user still needs to manually test the device to verify that it is working. Furthermore, the device is normally closed, making the contacts “hot” and hazardous.
Another electrical safety concern is fire resulting from arc faults or appliances malfunctioning. None of the aforementioned solutions address the problem of fire detection, or prevention. One source of fires is an arc fault. An arc fault may be a parallel fault, that is a discharge arcing between the hot line and neutral line, resulting from defects such as lack of insulation between the hot line and neutral line. A series fault is another type of discharge event resulting from defects such as a broken line, loose connection or other single wire failure. A ground arc results from loose grounding straps, shorts to ground and worn insulators. Any of these types of arcs create sufficient heat to cause a fire. A fire can also be caused by a degrading device such as an electric motor overheating. Although many of these causes of fires could be prevented with proper maintenance the defects, are either overlooked or not detected. The ability to measure temperature, detect an arc fault or detect a degrading or failing device would be beneficial.
Another concern today is energy conservation which relates to power consumption. Smart meters utilized by utility companies, although reporting in real time, only provide consumption information for an entire account, and not at the device level. A failing or overloaded device for example may consume more power than it should or more power than it historically has. An example of monitoring energy consumption at the device level is to monitor consumption at a receptacle. One advantage of this is the ability to measure the power being consumed by a failing device. It would be advantageous to provide a system for monitoring energy consumption at a receptacle.
Still another concern is the quality of power in the system. Poor power quality can be traced back to the electrical utility company or by interference from a device. In either case, these power disturbances resulting in poor power quality may cause device failure or damage to sensitive electrical devices.
Thus, it is desirable to provide an intelligent switchable device that can produce a signal indicative of the condition of a branch circuit, monitors and reports power consumption at the receptacle, detects arc faults and electrical problems as well as power disturbances. Additionally, it is also desirable to provide a receptacle that is normally open until a plug is engaged into the load side. Finally, it is also desirous to provide a receptacle that can communicate the device's state to external devices.